What is the relationship between pesticide occupational exposure and suicide rates?

Introduction
Introduction: The association of pesticide use and increased suicide risk is very controversial . An ecological study done in Brazil showed increased rates of suicide among workers in the primary sector (mainly farmers). Brazilian Ministry of Health data confirmed an increase in rates for small municipalities. However they were not able to identify the causes.
Objectives: To investigate the possible association between pesticides (occupational exposure and / or intoxication) and suicide rates.

Methods
Methods: We conducted an ecological study using as unit of analysis the 558 Brazilian micro-regions. The exposure data were obtained from Census 2000 and from 2006 Census of Agriculture (Federal Statistics Institute). Suicide data from the 2006-2008 triennium were examined for male, female and both sexes, age-standardized according to WHO standard population. The proportion of rural properties that used pesticides and / or reported cases of pesticide poisoning in 2006 were evaluated as the main exposure. Statistical analysis were carried out using the Pearson correlation coefficient and multivariate linear regression, adjusting for demographic and socioeconomic factors (sex, age, religion, skin color, education, level of mechanization and farm size).

Results
Results: 26,835 suicides occurred in the analyzed period, with an annual average of 8,945 cases and a ratio male:female 3.8. Pesticide exposure and pesticide poisoning showed positive correlation with suicide rates. Micro-regions with higher proportion of farms that used pesticides, as well as those that presented higher proportion of pesticide poisoning had higher rates of suicide for male, female and both sexes (p value from 0.01 to <0.001).

Discussion
Discussion: This study reinforces the hypothesis that pesticide use and incidence of pesticide poisoning could increase suicide rates. However, due to the limitations of ecological design such as the ecological fallacy further studies are necessary, using appropriated design to confirm the causality relationship.